In order to store digital electronic data it is known to use magnetic tape cartridges comprising a pair of reels, which are inserted into a tape drive unit having a plurality of read/write heads. Typically, such magnetic tape storage devices may be used to back up data generated by a host device, eg a computer, or to store data generated by test or measurement instruments. For example, the conventional SureDrive.RTM. data storage unit manufactured by Hewlett Packard Company is capable of storing 8 GBytes of data on a single cassette cartridge. In the conventional SureDrive series 12000 unit, by including a plurality of cassette cartridges, a data storage capacity 48 Gbytes is achieved in a single compact drive assembly of dimensions of the order of a few tens of centimeters.
Conventional tape drive units operate to draw an elongate magnetic tape past a read/write head. Tape speeds past the heads are relatively slow, of the order of a few centimeters per second.
In the conventional tape drive, electronic circuitry is provided to encrypt the digital data to be stored, using an algorithm which applies redundancy encryption to the original digital data, so that the data recorded on to the magnetic tape incorporates redundant data from which the original data can be recovered if there is corruption of the data recorded on the tape. Such corruption may occur at the edges of the tape due to non-uniform coating of the tape with magnetic material, or due to variations in alignment of the tape with the read/write head.
An on-going objective of magnetic tape drive development is to increase the amount of data which can be stored on a magnetic tape, and to reduce the size of tapes and tape drives thereby allowing drives to be used in an increasing range of applications. Achieving such objectives involves increasing the density of recorded data per unit area of tape.
However, as data density is increased and tape sizes become smaller, loss of data due to tape damage caused by tape stretching, or scratching of the tape becomes more problematic as any such damage may obliterate larger amounts of data.
It is another ongoing objective of tape drive development to increase the reliability of tapes and tape drives whilst reducing their cost.